Some friends of mine keep recommending Viticulture, and they've played it regularly as a date-night game with just the two of them. I haven't ever gotten around to playing it, though, so I don't know if it's any good. It's got a pretty respectable 8.0 on boardgamegeek, though.
2 players: 7 Wonders Duel, Hive, Schotten Totten, Sobek: 2 Players, Cribbage.
4 players, also great for 2 and 3 players: Arboretum, Azul, Calico, Gizmos, Happy Little Dinosaurs (good for younger kids), Photosynthesis, Shifting Stones, Sprawlopolis, That's Pretty Clever!, War Chest.
My Girlfriend and I play a lot of 2 player games. 7 Wonders Duel and Schotten Totten are our personal favorites. Calico and Arboretum are also a lot of fun.
Azul is better with 2-3 players than at 4.
Others that play well with 2 & 3 players: Dominion Race for the Galaxy Castles of Burgundy
I have Dominion and RftG. I may just have to get back into them. Thank you.
Just remember to take out cathedral :)
All things relating to and about tabletop gaming and board gaming generally!
See also Tabletop Gaming's sister community Gaming.
This community's icon was made by Aaron Schneider, under the CC-BY-NC-SA 4.0 license.